(Edit October 13, 2015 This thread has changed considerably since i started it with the intention of showing how the sound of Stax phones could be improved by using sorbothane on various portions of the earcups. Several other Headfiers have joined in to discuss the use of sorbothane and even some other materials to achieve these improvements on Stax and various other phones. This is all to the good in my opinion because it has gradually become evident that there is a problem of undamped mechanical resonance in many, if not all headphones. The more phones which are studied the more we will come to understand the nature of the underlying issues of mechanical resonance. It is clear that this is no longer simply an issue for Stax or even electrostatic phones. My efforts and those of others to come up with damping strategies with Stax phones are found in the earlier posts. Whenever I have modified my methods, I have edited the posts for those phones, including the Stax Lambdas, SRX III pro, Sigma/pro, SR007 and SR003 so what is there should represent my latest take. I am trying to get another thread started to explain this problem. It is taking me a while to get this together, although there are snippets of explanations scattered throughout this thread and the previous thread dealing with the SR007 ) I have been toying with a write-up of my efforts to damp the vibrations in the earcups of various Staxen by sorbothane, something I have been playing with for almost 1/1/2 years. I realized that it was going to take a long posting to cover the 007A, 003, SRX3 Pro, Sigma Pro, Sigma/404 , Lambda LNS and Lambda 404 and that I was just not going to get it done. That plus the fact that I am still experimenting and have by no means fully explored this phenomenon to my satisfaction. However, I am reasonably happy with what I have done with the Lambdas and as these are probably the most common Staxen I thought it would be worth reporting these first. EDIT 5/28/15 - When I started this work I did not have much more to go on than that I had found that under some circumstances the application of sorbothane to the earcups or other parts of some headphones could make an almost remarkable change in their sound. Now I realize that as important as that may be, more significant is the fact that doing anything to the body of the phones could markedly change their sound. I now believe this means that there is a large amount of mechanical energy floating around most phones, which is insufficiently damped and which is messing up the sound of even the best phones. Even more remarkable is that this phenomenon has either not been observed before or been ignored by even the top headphone makers. I will develop this argument at a later time, although portions of it are scattered throughout this thread. I am keeping the current thread for discussions of what may be the more effective types of sorb mods for the various Stax phones I own. I got started on this issue when I noticed that the arc assembly of the 007A appeared to impact the sound of these phones. http://www.head-fi.org/t/671314/stax-sr007-resonance-problems I will grant that the first reaction of anyone who looked at this posting was very likely What? It is odd to claim that the headband has an impact on sound. But that's what I heard. I put together a simple damping mechanism using sorbethane and a plastic clamp, played with it, liked what it did to the sound and left it alone for many months. (EDIT: so far I have only heard this on the 007, but cucera has recently reported damping the headband of the 4070, which looks like it has much the same kind of band arrangement as the 007, i.e it screws directly to the earcups. Other Stax headbands, have at least one other segment separating the headband from the earcups and that, I used to believe, makes a big difference. Now it is more evident that it is easy for vibrations to travel across most headbands. Companies including B&W and Audioquest are specifically working on this problem. After a while it dawned on me that even though the arc assembly may have been vibrating during the playing of music, the real problem had to be where the vibrations were coming from, presumably the earcups themselves since that was where the energy originated. I.e. there was energy floating around the earcups which was making it to the 007A arc assembly because of the way the earcups were tightly screwed to the arcs. If so, was there a similar issue with other Stax headphones and how could you find out? After an even greater time I started playing around first with a Sigma Pro by putting a strip of sorbethane across the bottom front of the earcups. It made the sound awful. The bass could only be described as flatulent i.e a bass fart. There may have been some increased clarity in the upper and mid frequencies but the awful bass squelched this experiment. However it did show that something was going on in the cups and I did eventually come up with a reasonable fix for the Sigmas. But I am still playing with it so I don't want to discuss it first. The Lambdas were a lot easier. There is room on the baffle board that holds the transducer to attach strips of sorbethane around the drivers. I used self-stick sorbethane about 1/8 inch thick. (EDIT I am now using 1/4 inch 70 duro sorbothane, cut into small segments with no dimension longer than 3/4" to 1. I am also playing with 1/2 " sorb but this is very difficult to locate on many phones, but is even better. The 1/8 inch is good but the 1/4" is better, and the small segments appear better than the longer segments noted in the original pictures.You can buy this stuff on ebay for a few bucks and it comes in various thickness down to 1 mm, with or without self-stick. It took about 10 minutes to install this on the Lambda LNS and 404s and because it's out of sight you would never know it's there. It may add an ounce or so weight to each cup. So what does it do to the sound? Makes it tighter, cleaner, gets rid of some fuzziness and brings out sonic detail including harmonics. It's hard to do a before and after comparison with the Lambdas because of the time it takes to install the sorbethane but I was able to do this with the Sigmas because with these the sorbethane was simply stuck to the outside of the cups ( after I got an arrangement that I thought sounded good) and could be just peeled off. With both Sigmas, upon ripping off the sorbothane suddenly there was a jump in sound level, in which an odd ambience suddenly appeared. It wasn't unpleasant but it probably wasn't music either. It adds a fair bit to the volume though and probably ends up masking the sound coming from the drivers. This, I think is resonance which is getting damped by the sorbothane resulting in a lower overall signal. With all of the Stax I have tried with sorbothane, I find I am turning up the volume more. (but enjoying what I hear more too) So what have I got here? A possible tweak with Stax phones. It could work with others but I don't have anything else. I would be especially curious to know if dynamic phones are affected this way. And as I stated in the beginning, these are merely first efforts. There are obviously a lot of parameters to play around with such as the location of the damping material, how much to use, its thickness, how it is fastened (I am still working on clamps so that the pressure can be adjusted) and whether there might be other materials which could work better. Sorbothane also comes with different levels of stiffness (duro) so presumably this is a factor too. EDIT A number of people have been reluctant to open them up to put sorb inside. However there is little or no other place on the earcups to put any significant amount of sorbothane. On other phones, you can place it outside but the Lambdas have almost no solid surface to do this, except the baffle. The lambdas are not that hard to open. For a start you don't need to remove the earpads, such peel them back a bit and unscrew the corner screws. The baffle may be somewhat stuck. Stax does not glue them as should be obvious from the use of 4 screws to hold the baffle in place. However the baffle can feel stuck, possibly because glue from the earpads gets in to the space. However, a bit of careful prying will get the baffle out. Lift the baffle a few millimeters all around and then lift it up along with the section where the cord enters the earcup and voila you are ready to go.